To design a typical custom lapel pin for a city, it is better to collect more information about it.
As you can imagine, how you do without any knowledge about it.
As you can imagine, how you do if you did not go there?
As you can imagine, how you do if you don't like it.
You may can't make a good design even if you like this city, but if you don't like the city, certainly you won't make out a epic design.
Fist, let's check the history of the Ottawa city.
With the draining of the Champlain Sea around 10,000 years ago the Ottawa Valley became habitable. The area was used for wild edible harvesting, hunting, fishing, trade, travel, and camps for over 6500 years by local populations. The Ottawa river valley has archaeological sites with arrow heads, pottery, and stone tools. The area has three major rivers that meet, making it an important trade and travel area for thousands of years. The Algonquins called the Ottawa River Kichi Sibi or Kichissippi meaning "Great River" or "Grand River"
And then, check the environment, more detail more better.
Ottawa is situated on the south bank of the Ottawa River and contains the mouths of the Rideau River and Rideau Canal. The older part of the city (including what remains of Bytown) is known as Lower Town, and occupies an area between the canal and the rivers. Across the canal to the west lies Centretown and Downtown Ottawa, which is the city's financial and commercial hub. As of 29 June 2007, the Rideau Canal, which stretches 202 km (126 mi) to Kingston, Fort Henry and four Martello towers in the Kingston area was recognized as a UNESCO World Heritage Site.
Located on a major, yet mostly dormant fault line, Ottawa is occasionally struck by earthquakes. Examples include a magnitude 5.2 earthquake on 1 January 2000, a magnitude 4.5 earthquake on 24 February 2006, a magnitude 5.0 earthquake on 23 June 2010, and a magnitude 5.2 earthquake on 17 May 2013.
From the map, check the city shape, you can design a pin shape base on this city shape. The mountain or river may be your source of inspiration.